This invention relates to thermographic transfer recording media generally and, more particularly, to those capable of producing an image having rich gradation and excellent preservability on an image receiver.
In thermographic transfer recording apparatus such as thermal printers, thermal facsimiles and the like, a thermographic medium is used to produce and transfer an image onto an image receiver, such as plain paper. To obtain these transfer images, it has been known to heat a material containing a sublimable dye, pigment or the like whereby the dye or pigment is sublimed, fused, or volatilized to produce an image on an image receiver.
However, there are substantial disadvantages in a thermographic transfer recording medium using a sublimable dye. Preservability is poor because the dye density of the transferred image varies moment to moment as a result of the sublimation of the dye, not only before recording, but after as well.
Thermographic transfer recording media using thermally fusible material containing a pigment or the like are advantageous because the preservability is excellent; however, this is offset by the substantial disadvantage that image gradation cannot be shown by changing the optical density of a transferred image per unit transfer area in accordance with the quantitative variations of an image forming material.
Meanwhile, Japanese Patent Publication Open to Public Inspection (hereinafter OPI) No. 68253/1979 has proposed a thermographic transfer recording medium having a finely porous layer comprising a resin and an ink component capable of being fused by heat. This recording medium has also been found to be disadvantageous; its thermal transfer efficiency is poor, fully satisfactory transfer density is not obtainable, unevenness on a transfer image is conspicuous, and image gradation can hardly be obtained.